Solvent recovery methods

The lack of satisfactory solvent recovery methods prior to 1930 prevented the use of selective solvents more suitable for lubricating oils. The major part of any solvent extraction plant is its complex solvent recovery system. Chemical engineering s contributions to distillation theory and process design resulted in the development of efficient solvent recovery techniques. In 1933, as illustrated by Figure 3, large commercial plants were... 

With more recent solvent recovery methods the consumption of alcohol and... 

In the absence of a solvent-recovery method, entrainment is expected to be the major solvent-loss factor in all solvent-extraction applications [94], including CSSX [89], potentially amounting to several hundred ppm of the aqueous effluent. Solvent loss is known to be the economic determinant in most commercial solvent-extraction systems... 

The number of solvent recovery applications is small primarily because ED cannot, except in a few specialized cases, be carried out batchwise. This tends to limit ED to comparatively large streams. Such streams do not arise in solvent recovery until a process approaches maturity, at which point there is likely to be resistance to changing solvent recovery methods. 

Optimization. Optimi2ation of the design variables is an important yet often neglected step in the design of extractive distillation sequences. The cost of the solvent recovery (qv) step affects the optimi2ation and thus must also be included. Optimi2ation not only yields the most efficient extractive distillation design, it is also a prerequisite for vaUd comparisons with other separation sequences and methods. 

Degreasing small parts can be achieved with solvent sprays. Chlorinated hydrocarbons such as trichloroethylene (tricho) are sometimes used, normally in a heated vapor bath, although special handling, solvent recovery, and disposal methods are required. 

Distillation is a well-known process and scale-up methods have been well established. Many computer programs for the simulation of continuous distillation columns that are operated at steady state are available. In fine chemicals manufacture, this concerns separations of products in the production of bulk fine chemicals and for solvent recovery/purification. In the past decade, software for modelling of distillation columns operated at non-steady state, including batch distillation, has been developed. In the fine chemicals business, usually batch distillation is applied. 

The most obvious way of recovery of substances from the layer is to extraet the adsorbed substanees from the adsorbent with a suitable solvent (indireet method). The solvent is then evaporated, and the remaining sample is analyzed or... 

The study concluded that Once wash steps are optimized, samples prepared by solid phase extraction are cleaner than those prepared by protein precipitation. Samples prepared by extraction with a Multi-SPE plate resulted in lower LOQs than samples prepared by solvent precipitation. Drug recoveries were acceptable (>80%) for both the SPE and the solvent precipitation methods. Well-to-well reproducibility of samples was slightly better with extraction with a Multi-SPE plate. Evaporation and reconstitution, while more time-consuming, yield better chromatographic performance, allow analysis of lower concentration samples, and require optimization for good analyte recovery. 

Quality Assurance/Quality Control. QA/QC measures included field blanks, solvent blanks, method blanks, matrix spikes, and surrogates. Percent recovery was determined using three surrogate compounds (nitrobenzene-d5, 2-fluorobiphenyl, d-terphenyl-diQ and matrix spikes (naphthalene, pyrene, benzo[ghi]perylene) the recoveries ranged from 80 to 102%. Separate calibration models were built for each of the 16 PAHs using internal standards (naphthalene-dg, phenanthrene-dio, perylene-di2). Validation was performed using a contaminated river sediment (SRM 1944) obtained from NIST (Gaithersburg, MD) accuracy was <20% for each of the 16 analytes. 

A completely automated system with reinjection/sample collection and solvent recovery allows the separation of up to 10 g of extract a day. The Cjq is obtained in very high purity and the recovery is nearly 100%. A simple benchtop method for the enrichment of preparative amounts of Cjq, C7Q and higher fullerenes (up to Cjqq) from a crude fullerene mixture is based on a single elution through a column of poly(dibromostyrene)-divinylbenzene using chlorobenzene as mobile phase [208]. 

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